Rhubarb Tosca Bun Cake - Raparperi-toscapullakakku

Last week I learned something about custards. I don't remember having a problem like that before. I made a custard the usual way, though it seemed to get thick straightly after adding the hot milk. I still returned it back to the stove, but it was so thick I had to add more milk (maybe 50-75ml) to make it more stir-able. It remained thick still and once it had "burped" I took it from the stove, returned it to the plastic bowl and covered with a cling-film. The next morning it had turned into a liquid... I found out quickly that the problem might have been the enzymes in the egg (amylase mainly). You need to bring egg/starch mixes to a full boil to inactivate the amylase from the yolk, which will otherwise liquefy the custard eventually (the amylase enzyme breaks down amylose, present in starch giving the custard some of its structure and thickness). The custard should "burp" (=boil) and be kept there for a minute or two (not sure if potato starch can handle this, but corn starch will) stirring constantly with a whisk. This is important if you want the custard to stay firm for a few days, as the amylase will work on it over time and make it increasingly liquid.

But please remember: you don't want to coagulate the yolks any more than needed (80-82C when in liquid), starch to gelate (62-80C) and to inactivate the amylase in the yolks (takes a minute at the boil). Therefore, once everything coagulates and starts to burp, cook it only the minimum length of time so that the yolk doesn't overcook. If you are serving the custard immediately, I wouldn't care about the amylase, as not boiling the custard results in a more silky texture.

Then something about the cake itself: I've been planning ages to try making Bienenstich Cake aka Bee Sting Cake. It reminds me of Finnish Tosca Cake, which is a cake with an almond caramel topping. Though bienenstich is traditionally made with yeasted dough as opposed to tosca cake which is made with cake batter. This cake got its inspiration from Bienenstich, but I wanted it to have more cake versus filling, so I followed smitten kitchen's recipe loosely (made the yeasted dough with my own recipe, though).

Oh, and to return to my problem with the custard, all ended well, I mixed more potato starch with a small amount of custard and whisked that to the rest of the custard, then warmed it until thick and let it "burp" a minute. This time it remained thick.

And then a word on the tosca topping. In the Finnish tosca cake usually no honey is added. And it's never sticky while this one remained sticky. There is usually also a small amount of wheat flour, which might also take some of the stickiness away. Next time I would try either one. If you do, please tell me how it went.

Rhubarb & Tosca Yeasted Cake aka Rhubarb Bienenstich

Yeast dough:
200 ml milk
20 g fresh yeast or 5 g instant yeast
1/2 Tbsp cardamom
65 g sugar
n.1/4-1/2 tsp salt
n. 350 g bread flour
60 g butter

Tosca topping
40 g butter
50 g sugar
1 Tbsp honey
1 Tbsp milk
60 g almond flakes

Vanilla custard/Crème pâtissière:
350-400 ml milk (or a mixture of cream and milk)
1/2 vanilla pod
3 egg yolks (appr. 53 g)
30(-40) g potato starch
25 g sugar

For filling:
200-300 ml rhubarb compote (see recipe below)

Crumble the fresh yeast to a bowl (or if using dry yeast, mix it with appr. half of the flour). Warm up the milk to 37 C. Add it gradually to the fresh yeast to dissolve it completely before pouring on the rest. Add sugar, salt and cardamom. Add the bread flour little by little (if using dry yeast, use first the half containing the yeast). When the batter resembles thick pancake batter beat it for some time in order to get some air into the dough and to gain elasticity. Add more flour to obtain a smooth dough that starts to unstick from the bowl. Add soft butter and knead the dough until butter is well incorporated. Add more flour if needed. Cover the dough with a cling-film or cloth and let it rise in a warm place until doubled in size (appr. 45 minutes depending heavily on the temperature).

Punch the dough down and knead it on a floured surface. Roll it into a slightly bigger disc than your cake pan (over 24 cm in diameter). Cut it to proper size (cutting ensures a more even result with the cake) and put to the cake pan. Let rise under a cloth appr. 20 minutes. While they are rising, warm the oven to 175 C.

Make tosca: Cook all ingredients for a few minutes. Let cool slightly before spreading on the risen cake. Bake in 175 C for 30 min. If the almonds start to get too dark, cover with a baking paper. Let cool completely.

Make vanilla custard (can be made in advance): Halve the half of the vanilla pod and scrape the seeds to a pot. Add milk and bring to a boil. Take off the heat, and let simmer for 10-15 minutes.
Whisk egg yolks with sugar and potato starch. Remove the pod from milk and bring to a boil again. Pour it while whisking to the egg mixture. Pour it back to the pot, and warm it on medium-high heat while stirring until it thickens and "burps". Let cool. You can speed the cooling up by placing the pot to a cold water bath. Cover with cling-film placed directly on the surface to prevent a skin forming.

Halve the cake into two (the bottom part can be slightly thicker). Fill with rhubarb compote and vanilla custard. The vanilla custard should be so thick that it doesn't pour out when cutting the cake.

Rhubarb compote:
250 g rhubarb
50 g sugar
1/2 tsp ground cardamom

Cut the rhubarb into chunks and cook it in a pot with sugar and cardamom for 10 minutes. Let cool. (If it's very wet, you can try sieving some of the juice away and cooking it to thick syrup, which you can add back to compote.

Raparperi-toscapullakakku eli Raparperi-Bienenstich

Pullataikina:
2 dl täysmaitoa
n. 2/5 paketillista tuorehiivaa
1/2 rkl kardemummaa
0,75 dl sokeria
n.1/4-1/2 tl suolaa
n. 5 dl jauhoa
60 g voita

Toscakuorrutus:
40 g voita
60 ml sokeria
1 rkl hunajaa
1 rkl maitoa
1,75 dl mantelilastuja

Täytteeksi:
2-3 dl raparperihilloketta (ks. ohje alla)

Vaniljakiisseli eli crème patissière
3,5 dl täysmaitoa (tai kermamaitoa)
1/2 vaniljatanko
3 keltuaista (n. 53 g)
20 g perunatärkkelystä
25 g sokeria

Tee pullataikina, anna kohota kaksinkertaiseksi. Poista ilma, ja kaulitse levyksi. Leikkaa esim. kakkuvuoan reunoilla n. 24 cm ympyrä. Anna kohota.

Tee toscakuorrutus: Keitä kaikkia aineksia muutama minuutti. Anna jäähtyä hetki (ei liian kauan, koska se muuttuu hankalaksi kaataa. Kaada kohonneen kakun päälle toscakuorrutus ja paista n. 175 C n. 30 min. Jos kuorrutus uhkaa tummua liikaa, peitä pinta leivinpaperilla. Anna jäähtyä ennen halkaisemista.

Tee vaniljakiisseli: Halkaise vaniljatanko ja raaputa siemenet kattilaan. Kiehauta (kerma)maito vaniljatangon ja -siemenien kanssa, ota pois lämmöltä ja anna maustua 10-15 min. Poista tanko. Vaahdota keltuaiset, sokeri ja tärkkelys. Lämmitä maito uudelleen kiehuvaksi ja vatkaa keltuaisseoksen joukkoon. Kaada seos takaisin kattilaan, ja lämmitä varovasti samalla sekoittaen, kunnes se sakenee ja "pulpahtaa" kerran. Jäähdytä kylmässä vesihauteessa samalla sekoittaen.

Halkaise kahteen osaan. Täytä raparperihillokkeella ja vaniljakiisselillä. Anna makujen tasaantua muutama tunti ennen tarjoilua. Ohjeen vaniljakiisseli on niin paksua, että kakun leikkaamisen tulisi onnistua ilman täytteen suurempia pursuiluja välistä.

Raparperihilloke:
250 g raparperia
50 g sokeria
1/2 tl kardemummaa

Paloittele raparperi ja keitä sitä n. 10 minuuttia sokerin ja kardemumman kanssa. Anna jäähtyä. Jos hilloke on vetistä, siivilöi osa mehusta pois ja keitä sitä, kunnes siitä tulee siirappisen paksua. Sekoita takaisin hillokkeen joukkoon.

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